In the UMTS (Universal Mobile Telecommunications System) that has been standardized as a third-generation mobile communication system, an MT (Mobile Terminal) is established as a mobile terminal that has a UMTS wireless interface and a TE (Terminal Equipment) is established as a terminal equipment that connects to the MT. The MT and TE are collectively called UE (User Equipment).
A TE-MT interface is set forth in the Non-Patent Document 1 (TS 27.060), wherein a communication protocol is indicated in which a TE such as a laptop PC (personal computer) that does not have a UMTS wireless interface connects to a PDN (Packet Data Network) that is an external network, via the UMTS wireless interface in an MT. Although the physical interface between the TE and MT can use not only a wired interface such as a serial cable or a USB (Universal Serial Bus) cable, but also can use a wireless interface such as Bluetooth (registered trademark) or the like, the use of the PPP (Point-to-Point Protocol) is called for.
Patent Document 1 discloses a method whereby, rather than a TE-MT interface, an Ethernet (registered trademark) and DHCP (Dynamic Host Configuration Protocol) are used to allocate an IP (Internet Protocol) address to the TE and make connection to the PDN. Additionally, it is assumed that it will be possible to use this TE-MT interface in the EPS (Evolved Packet System), which is standardized as the next-generation mobile communication system by the 3GPP (3rd Generation Partnership Project).
The protocol for connecting a UE to the PDN in an EPS is set forth in the Non-Patent Document 2 (TS 23.401). The UE, after first being attached to the wireless access network, establishes a logical path connection to the PDN, which is known as a PDN connection.
The PDN is uniquely identified by the APN (Access Point Name), and is connected to the core network via a PDN-GW, which is an external gateway equipment. The PDN connection is established individually for each PDN-GW that is connected to the UE. Even via one and the same PDN-GW, when connections are made to different PDNs, independent PDN connections are required.
One PDN connection combines a plurality of logical paths that is known as an EPS bearer when transferring a user IP packet, and it is further possible to assign a QoS (Quality of Service) class and a charging rule or the like to each EPS bearer. Therefore, using the UE packet transmission destination and transport protocol, it is possible to apply different QoS classes and charging rules to each IP packet, using a port number.    Patent Document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2008-511222    Non-Patent Document 1: TS 27.060 Packet Domain; Mobile Station (MS) Supporting Packet Switched Services    Non-Patent Document 2: TS 23.401 General Packet Radio Service (GPRS) Enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Access